Scientists uncover room-temperature route to improved light-harvesting and emission devices

(Press-News.org) HOUSTON – (Sept. 30, 2025) – Atoms in crystalline solids sometimes vibrate in unison, giving rise to emergent phenomena known as phonons. Because these collective vibrations set the pace for how heat and energy move through materials, they play a central role in devices that capture or emit light, like solar cells and LEDs.

A team of researchers from Rice University and collaborators have found a way to make two different phonons in thin films of lead halide perovskite interact with light so strongly that they merge into entirely new hybrid states of matter. The finding, reported in a study published in Nature Communications, could provide a powerful new lever for controlling how perovskite materials harvest and transport energy.

To get a specific light frequency in the terahertz range to interact with phonons in the halide perovskite crystals, the researchers fabricated nanoscale slots ⎯ each about a thousand times thinner than a sheet of cling wrap ⎯ into a thin layer of gold. The slots acted like tiny metallic traps for light, tuning its frequency to that of the phonons and thus giving rise to a strong form of interaction known as “ultrastrong coupling.”

“To our knowledge, this is the first room-temperature demonstration in a perovskite thin film where two phonons enter the ultrastrong coupling regime with a single engineered terahertz resonance,” said Dasom Kim, a Rice doctoral alumnus who is a first author on the study.

In order to tune the effect, the researchers made nanoslots of seven different sizes: Longer slots trapped lower-frequency light, while shorter ones trapped higher frequencies. The goal was to precisely match the confined light frequency to the vibration frequencies of the perovskite material.

“We fabricated arrays of nanoscale slots with seven slightly different lengths to tune a single terahertz resonance and deposited perovskite thin films on top,” Kim said. “Designing the slot geometry allowed us to shape the interaction between light and the perovskite phonons without using high-power laser pulses or bulky crystals.”

The payoff was the appearance of three distinct hybrid quantum states known as phonon-polaritons, each a new blend of vibration and light.

“The coupling ratio reached roughly 30% of the phonon frequency at room temperature,” Kim said.

The ability to stage such strong, exotic interactions between multiple quantum modes without resorting to external driving factors opens the door to new ways of steering energy flow in optoelectronics.

The experimental results were validated by numerical simulations and a theoretical quantum model, which allowed the researchers to calculate the actual coupling strengths and confirm that the two phonon modes were indeed operating in the ultrastrong coupling regime.

“Advances in nanofabrication and perovskite film quality made it possible to reach this regime reliably,” Kim said.

“This offers a gentle, device-compatible way to influence processes that matter for light harvesting and light emission, potentially improving performance and reducing energy losses,” said Junichiro Kono, the Karl F. Hasselmann Professor in Engineering, professor of electrical and computer engineering and materials science and nanoengineering and the corresponding author on the study.

“What makes this result stand out is that we were able to uncover entirely new phonon behavior without extreme conditions just by carefully designing the nanoscale environment,” added Kono, who also serves as director of the Smalley-Curl Institute at Rice.

The research was supported by the U.S. Army Research Office (W911NF2110157, W911NF2210158), the W.M. Keck Foundation (995764), the Gordon and Betty Moore Foundation (11520), the Robert A. Welch Foundation (C-1509, C-2144), the Air Force Office of Scientific Research (FA9550-22-1-0408), the National Science Foundation (2246564, 1943895) and the Singapore Ministry of Education (MOE-MOET32023-0003). The content herein is solely the responsibility of the authors and does not necessarily represent the official views of the funding organizations and institutions.


-30-

This news release can be found online at news.rice.edu.

Follow Rice News and Media Relations via Twitter @RiceUNews.

Peer-reviewed paper:

Multimode phonon-polaritons in the ultrastrong coupling regime | Nature Communications | DOI: 10.1038/s41467-025-63810-7

Authors: Dasom Kim, Jin Hou, Geon Lee, Ayush Agrawal, Sunghwan Kim, Hao Zhang, Fuyang Tay, Shengxi Huang, Elbert E. M. Chia, Dai-Sik Kim, Minah Seo, Aditya Mohite, David Hagenmüller and Junichiro Kono

https://doi.org/10.1038/s41467-025-63810-7


Video is available at:

https://www.youtube.com/watch?v=a8QiMaz0CyQ

Download photos at:

https://rice.box.com/s/u1ircrhzlfhhr2vt83ehcsft8glkjhc5

(Video and photos by Jorge Vidal/Rice University)


About Rice:

Located on a 300-acre forested campus in Houston, Texas, Rice University is consistently ranked among the nation’s top 20 universities by U.S. News & World Report. Rice has highly respected schools of architecture, business, continuing studies, engineering and computing, humanities, music, natural sciences and social sciences and is home to the Baker Institute for Public Policy. Internationally, the university maintains the Rice Global Paris Center, a hub for innovative collaboration, research and inspired teaching located in the heart of Paris. With 4,776 undergraduates and 4,104 graduate students, Rice’s undergraduate student-to-faculty ratio is just under 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for lots of race/class interaction and No. 7 for best-run colleges by the Princeton Review. Rice is also rated as a best value among private universities by the Wall Street Journal and is included on Forbes’ exclusive list of “New Ivies.”

END